The present invention relates to mobile communication systems and more particularly to a method of operating a mobile communication device within a geographical area having overlapping coverage from first and second mobile telephone networks, where said first network is the home network of the mobile communication device and said first and second networks provide respective first and second sets of services. The present invention also relates to a system for performing this method of operation.
A number of digital mobile telephone standards are in use throughout the world. These include the European GSM standard and the US TDMA standard. However, due to the ever increasing demand for mobile telephone services many, if not all of these standards are likely to be superseded by new standards offering increased network capacity and/or increased data transmission rates. In particular, the European Telecommunications Standards Institute (ETSI) is currently developing a so called third generation mobile environment known as the Universal Mobile Telecommunication System (UMTS) which it is expected will be operational by 2002. UMTS will operate in the 2 GHz frequency band and will offer data transmission rates of up to 2 Mbits/sec, compared to a rate of only 9.6 Kbits/sec offered by the existing GSM standard.
In the transition from second generation standards to third generation standards, there is likely to be a period when both second and third generation standards will have to coexist. It is also possible that such coexisting networks will be operated by different operators. As with all previous standards, networks implementing the new standards are likely to be introduced piece-meal, extending their geographical coverage over time. It may also be the case that the geographical coverage offered by third generation networks will always be less than that offered by second generation networks due to the need to sustain high bit rate transmissions with the former.
It is proposed (in Europe at least) to enable mobile stations registered with a third generation network as the xe2x80x9chomexe2x80x9d network (i.e. the network to which the mobile stations subscribe) to transfer to a second generation network when the stations are outside the coverage area of the home network, with appropriate cross-billing agreements between the network operators, to alleviate the possible geographical limitations. This transfer will operate in substantially the same way as the xe2x80x9croamingxe2x80x9d function of conventional GSM networks (GSM 03.22) where a station can register with an alternative network when the RF connection between the mobile station and the home network is too weak to support a traffic channel. Of course third generation terminals will have to be dual mode, e.g. UMTS/GSM, in order to take advantage of this facility.
The inventors of the present invention have addressed the problem of how mobile stations registered with earlier generation networks, e.g. second generation networks, as their home network may gain access to new services only available through new generation networks, e.g. third generation networks. This may be a requirement of reciprocal arrangements between second and third generation network operators. As far as the inventors are aware this problem has not been previously addressed.
According to the present invention there is provided a method of operating a mobile communication device within a geographical area having overlapping coverage from first and second mobile telephone networks, where said first network is the home network of the mobile communication device and said first and second networks provide respective first and second sets of services in said geographical area, the method comprising registering the device with said first network when a service of said first set is requested and registering the device with said second network when a service of said second set, but not of said first set, is requested.
Typically, although not essentially, the overall geographical coverage of said second network is less than that of said first network, as is likely to be the case in the period following the introduction of a new mobile telephone standard which is implemented by said second network.
Preferably, a service provided by said second network, but not by said first network, is a high transmission rate service, that is at a higher transmission rate than is possible with services provided by said first network. Examples of high bit rate services are internet browsing, videophone, and data downloading.
The request for a service may be made by the mobile communication device, e.g. in response to a user input, or by the first network, e.g. in response to an incoming call made to the mobile communication device. In either case, in the event that a service of said second set, but not of said first set, is requested, registration with said second network may be carried out automatically under the control of said first network. In this event, there is no need for the user of the mobile communication device to be aware of the change of registration. Alternatively, a decision on a change of registration may be made by a user via a user interface of the mobile communication device.
In one embodiment of the present invention, said first network is a GSM network and said second network is a UMTS network and said mobile communication device is a dual mode UMTS/GSM device.
According to a second aspect of the present invention there is provided a mobile telecommunication system comprising at least first and second mobile telephone networks having an overlapping geographical area of coverage and a multiplicity of mobile communication devices, wherein said first network is the home network of the mobile communication devices and said first and second networks are arranged to provide respective first and second sets of telephonic services in said geographical area, the system comprising control means for registering a communication device with said first network when a service of said first set is requested and for registering the device with said second network when a service of said second set, but not of said first set, is requested.
The control means may comprise means associated with each of the mobile communication devices for transmitting a deregistration request to the first network and for transmitting a registration request to the second network when a service of said second set, but not of said first set, is requested. Alternatively, the control means may comprise means associated with the first network for responding to a request from a communication device for a service of said second set, but not of said first set, by re-registering the communication device with the second network.
The mobile communication devices may be, for example, mobile telephones, combined mobile telephone/personal digital assistant devices, or other devices which use wireless telephonic communication.